Any experts on electrical substations??

We have just bought a house in a small rural village and around 5m from our house is an substation which i have looked up on western power shows it pumps out 11kw and has a hv capacity on 170kw. I rang up western power last night as i have noticed a hum from the unit and wondering if there is anything wrong with it, they are coming out in the next few days.

Can anyone put my mind at ease i have two very young children, and other than the obvious climbing up the fence, is there anything else i should be worried about with being close to it. I always new there was a substation when we bought the property but never noticed the hum til i read about it.

As above. 11kW of power is very little really, maybe enough for a few homes on average. As a reference I used to work with a 50kW power supply on my bench. The hum is just mechanical and you don't tend to hear it so much these days as most power supplies for equipment these days run at a much higher frequency that you can't hear

Your biggest risk is just worrying about it really and that is much more difficult to deal with. There are books (e.g. this one) or you could even buy a field strength meter but they may just make things worse by making you focus more on the 'problem'. I would just try and get used to it if you can. We have trains pass by the bottom of the garden and after a few months I no longer even hear them when they go by

A "substation" is a transformer. In is used to change the line voltage. because high voltages are used to transfer power over long distances (as it is more efficient). However, running your house on 11kV would be dangerous, as high voltage can "jump" or "arc" large distances.

So, these substations take the high voltage low current power and use a transformer to reduce that to a lower voltage but higher current.

The system runs on an alternating voltage at 50hz (50 cycles per second) and this sinusoidally varying voltage is used to create a magnetic field within the primary windings of the transformer. That field is then re-captured by the secondard windings and turned back into electricity (at a lower voltage in this case).

These transformers hum because the magnetic field causes parts of the transformer to vibrate (at 50Hz), just like a loudspeaker coil does. To maximise efficiency a typical transformer will be over 99% efficient, in effect much less than 1% of the magnetic field will "escape" and leak out.

Transformers tend to get noisier as they age, as when new all the windings and laminations in the core are tightly packed and well supported, but as they vibrate over the years they tend to get a bit looser and hum a bit more.

Crucially, magnetic field strength reduces with the square of the distance from the emitter, so if you are more than a foot or so from the transformer, the magnetic field strength leaking from it will be less than that created by the earths natural magnetic field!

In summary, unless it arcs, overheats then explodes, you are quite safe!

I'd guess that the fact "they are coming out in the next few days" means that everything is fine and they just said that to reassure you.
Try telling them you can see smoke and sparks and see how quickly they come out.

I work for western power and yes all subs do hum. Obviously i don't know how loud yours is so couldn't fully comment!
As for the kids i really wouldn't worry...the subs will be pretty secure and they would have to get in and start touching stuff to get a zap. Magnetic fields....i wouldn't worry especially as the voltages are relatively low..11,000 to 230v. I would be worried if you had one of the 400,000v national grid lines over your house.

In regard to transformers on poles and transformers on the ground in residential neighborhoods, probably not. The magnetic field is very high close to these units, but drops off rapidly as one moves away. At 4 to 5 feet the field is usually down to background levels, and people are seldom that close for a significant period of time. On the other hand, the wires feeding into and out of the transformer produce fields that may not drop off as quickly. The real question is: How close are these wires (underground or overhead) and how high is their field?

I would be worried if you had one of the 400,000v national grid lines over your house.

Go on...

please do tell as there is nice section of Bridleway/Singletrack near to my house which is directly under a section of high voltage power lines, scares me s#!t-less when its damp/raining; buzzing, crackling, so much so it’s become a weather dependant route.

mate of mine had one on nextdoor for many years then it got taken away and he bought the land for next to nothing and doubled his garage - not quite a fairy tale but a sort of happy ending - his kid plays drums in a band - make what you will of that

[If i lived close to a large substation or HV lines, i'd get busy building my own "field" capturing transformer to power my house for free!

(not sure if this is legally theft? After all, the electric field is leaking out anyway, i just happen to be capturing it afterwards? The same as putting a bucket under a leaky water main??)]

unfortunately thats wishfull thinking.... if they catch you they will prosecute....... although you may well burn your house down / fry yourself 1st.... if you don't earth one side of the windings your going to have some unpleasantly high pd's floating around....

I wouldn't be particularly worried about the electric or magnetic fields. Normally the fields will be stronger at your cutout (supplier fuse) than anywhere else on your property. This is simply because the incoming cable has greater current than the other circuits in your house and there is no shielding at the plastic cutout. Every house with electricity has one!

I assume it is a pole mounted transformer connecting an 11kV overhead line to the local LV (mains voltage) network?

If so make sure the kids don't climb up the pole, or throw things at it! Always keep a decent distance from any high voltage conductors.

If trees or bushes start to grow close to the bare metal conductors, phone the distribution network company. (saves you a power cut if they chop the undergrowth back before they grow into the line.) Also don't be tempted to do any tree surgery / hedge trimming / waving fishing rods or tent poles nearby!

What i said was i would be more worried compared to 11kv! Its still not been proven about any health problems although Im sure there was a program on tv about them years ago trying to. Some of you lot know alot more theory than i do anyway.!
Iv always been tempted to try the fluorescent light trick...looks pretty cool.

I find it very unlikely you are getting a shock from an oh line...it would have to be very low in which case i reckon you'd get more than a tickle!